A fire extinguisher is an apparatus for extinguishing fire utilizing cooling effect or oxygen cut-off effect of fire extinguishing agents.
Fire extinguisher is classified by its extinguishing capacity into a heavy duty extinguisher with an extinguishing capacity of 10 or 20 units or more, or a small extinguisher with an extinguishing capacity of one unit or more, but lower than that of a heavy duty extinguisher. A small extinguisher is often employed at households, work places, offices, etc. due to its convenience in carriage and transport.
A fire extinguisher can also be classified by the type of extinguishing agents filled in the main body thereof, into an acid-alkali extinguisher, an enforcement liquid extinguisher, a halogen extinguisher, a carbon dioxide extinguisher, or a powder extinguisher, and the like. Since fire extinguishing agents are in general of high price, fire extinguisher using extinguishing agents other than powder extinguisher are employed normally only at specific sites.
A fire extinguisher can further be classified by the type of pressure it employs, into a pressure extinguisher or a accumulate pressure extinguisher.
A pressure extinguisher, being a conventional technology, comprises a pressure gas container (also called, a “cartridge”) in the main body thereof where fire extinguishing agent is filled, as the container aims to press the extinguishing agent for injection. When a user presses two levers of the fire extinguisher until they are closely accessed to each other while the safety pin has been removed, the pressure gas container is opened, and the gas is released to press the extinguishing agent in the main body so that the extinguishing gas is injected out of the fire extinguisher.
However, a drawback of such pressure extinguisher is that its structure is complicated, because it requires a separate pressure gas container within the main body thereof, inclusive of a gas pipe for transmission of the pressure gas as well as an injection tube for the extinguishing agent.
Form this background, use of accumulate pressure extinguishers has been increased recently. For convenience of explanation, a fire extinguisher refers in the following description to a small powder fire extinguisher using accumulate pressure, if not mentioned otherwise.
An accumulate pressure type conventional fire extinguisher is consisted of a main body 110 with extinguishing agent and pressure gas filled in it, a head 120 installed at one end of the main body 110, two levers 122 fixed at the head 120, an extinguishing hose 130, one end of which is connected to the inside of the main body 110 while the other end is extended from the main body 110 to be exposed outward, and a nozzle fixed at one end of the extinguishing hose 130, as illustrated in FIG. 1.
At the two levers, a safety pin 124 is installed to prevent unintended access of the levers 122 to each other. Further, the head 120 is equipped with a pressure gauge 150 which indicates the pressure of the pressure gas consisted of nitrogen or carbon dioxide. The pressure gauge is one functioning mechanically with its indicator changing mechanically in accordance with the pressure changes inside of the main body 110.
In case fire occurs, a user removes the safety pin 124, presses the two levers firmly so that they are closely accessed, whereupon the extinguishing agent filled in the main body 110 is injected through the extinguishing hose 130 out of the nozzle 132, triggered by the pressure difference between high pressure in the tightly sealed main body 110 and low pressure atmosphere outside thereof.
However, since the main body of such conventional fire extinguisher is made of metal, it does not allow a user to confirm with naked eyes whether the extinguishing agent filled in is of prescribed quantity.
Another important factor for faultless functioning of such fire extinguisher is that the extinguishing agent filled in remain intact. In other words, the fire extinguisher fails to function when the extinguishing agent is hardened, even if the agent filled in is of sufficient quantity. A further problem with the conventional fire extinguisher is that it does not allow a user to confirm with his eyes whether the extinguishing agent filled in the main body thereof is in an intact state, i.e. not hardened.
Still another problem of the conventional fire extinguisher is that the pressure gauge installed at the lever part thereof to indicate the internal pressure of the main body is designed to function mechanically with a relatively high rate of malfunction, resulting in occasions when the fire extinguisher fails to function even if the inner pressure indicated by the gauge is normal. In addition, since such pressure gauge is exposed outward, it can easily be damaged by external force during carriage or transport.